Not for the faint of heart...


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Well, I guess I'm about to learn a hard lesson, maybe more than one. Truth is, I messed up, and I'm guessing this may end with me framing this plate as a warning instead of putting it on an instrument.

I was merrily shaving away at the inside of my back plate this evening, getting it down to around 3.5mm in places, when to my horror, I thought I saw the joint move against itself in the upper bouts. I took it out of the cradle and tried to move it, but it seemed solid. Went back to work, and once again saw the movement, and felt a cold, sick feeling in the pit of my stomach. Hope I'm not being overly dramatic, but this is what I've been fearing all along. I had been feeling rather proud of myself for finally getting a good joint, after all the effort I went through, but now it seems that feeling was rather premature. Long story short, holding the plate up to the light, and sure enough, there's light shining through that there seam. Pic below. Not pretty. Not real sure at this point if it's worse than it looks, but it looks plenty bad. Not sure if an experienced luthier would manage to save this, but fixing this may well be beyond my capabilities. I'll welcome any advice, even if it's "You screwed up, kid, go buy some more wood and try again..." (I kinda suspect that...).

seam.jpg

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Tim, You're killing me... I just glued up my front plate (for the second time this week) and was feeling pretty good about it until I read your post. Now I'm back to wondering....

I assume the seam looked pretty good before you started carving. I glued the front plates with a rubbed joint a couple of days ago and found a very small area near one end that I thought might not have received enough glue. The glue squeeze-out line tapered down to nothing on that side. I decided to saw it apart, rejoint it and glue it up again. I feel like I got really nice flat surfaces but I bet you did too.

I'm sorry it happened and I wish I could help but I'm kinda new to this. I will be watching with great interest for the answers to this one.

Well, thanks for being real and sharing this with us. Posting this sort of information will certainly keep us vigilant.

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I will tell you how to fix it and get back to work but the maestronet gods will be angry and I may get ostracized. But in the spirit of moving on, and if you are like me, to facing your next challenge, I will tell you how I would fix that.

This is a carry over from my guitarmaking experience.

Get some high quality, thin, cyanoacrolate glue (gasp) and have it ready. You only need a small amount and there are some better quality brands, but I have used the cheapo for different things and as long as it is thin, it usually seems to works fine. While you are at it buy some of the disolver while you are there just in case you glue your finger to something (don't ask).

Sand the area with fine sandpaper and push it into the crack, tap the plate to get the dust in the crack. Save some of the dust on a piece of white paper, or create some from an offcut and push it into the crack with a knife and leave a little above the surface if you can. Now drop some CA into the crack. It should dry in less than a minute, but to help it dry, exhale heavily onto it (humidiy in you breath will cure the glue). Scrape it flat and see if there is any light showing. You can repeat if necessary, it usually takes a couple times to fill a gap fully.

This fix is not really structural but more cosmetic, but will strengthen that area also. I would only use it on a small gap, not to compensate for a very badly fitting joint.

I hope I don't get spanked too bad for using CA.

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Sorry to bring such a downer, Chris, I hope you have better luck. Here's a better picture, I think, plus a picture of the affected area in the light. Yup, Chris, there were no indications at all until that slight movement started happening while planing. I guess I'll continue planing, and see if the problem is more widespread, or confined to this one area. Not sure it makes much difference...

seam2.jpg

seam3.jpg

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quote:


Originally posted by:
upnorth

I hope I don't get spanked too bad for using CA.

Hey, Ken, you posted while I was posting. Yeah, I know about CyA - I've built model airplanes for years. Sounds like it might work, depending. Sure as heck it isn't something anyone like Jeffrey would be caught dead doing, but he wouldn't be in this predicament in the first place. If it's the difference between hearing this plate make some kind of music, and seeing it on the wall, it'd be worth a try. Thanks for the tip!

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This happens all the time. Use hide glue.

You will find information in other threads here on closing cracks with pillars and clamps:

Crack Repair (link)

Oded's Clamps (link)

If the gap is too big to close easily (which for the moment I doubt), then there are ways to address that which will come up if needed I'm sure.

This Thread (link), contains some considerations for the latter case.

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Thanks, Andres. I was kind of daring to hope it might be possible to fix by traditional methods, like cleats or the like. Sounds like it might be okay after all. It wasn't going to be a great back, anyway, being my first. Guess I'll hope for the best until it shows me otherwise...

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I second what Andres says.

I don't think this is a train smash. It shouldn't even slow you down significantly.

PS - I wouldn't necessarily suspect the joint (either fit or glue) - how well is the plate supported from underneath the center while you are carving the inside?

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If something like that can easily be fixed by clamping , I would use hide glue also. I thought, and am still not sure if it can be clamped back together. It looks like a small micro gap that no amount of clamping could close. I was seeing a few small pinsized gaps and might have misinterpreted the problem.

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quote:


Originally posted by:
Jacob

PS - I wouldn't necessarily suspect the joint (either fit or glue) - how well is the plate supported from underneath the center while you are carving the inside?

I have a piece of 1" pine cut to the shape of the arch supporting the center seam lengthwise for interior carving. First thing I thought of.

quote:


Originally posted by:
upnorth

It looks like a small micro gap that no amount of clamping could close. I was seeing a few small pinsized gaps and might have misinterpreted the problem.

I guess I'll know when I set out to try clamping it. If it is a small gap, hopefully it can be compressed enough to glue it shut, then held in place with a couple of cleats. Of course, the cleats will have to wait until the graduation is done. After sleeping on it, I think the best course of action is to fix it now (short of cleats), to stabilize it, otherwise the act of graduating it will likely spread the problem and make it worse. If I'm very, very lucky, maybe the rest of the seam is good. Sure hope so. Lesson learned for next time...

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Even if it separated while graduating-- that is not a killer, though a real kick in the head. Finished violins occasionally pop the center joint-- what are you gonna do then? throw 'em out?

Of course it is fixable. Just not as fun as "everything went right on the first try."

And I concur with the others-- use the hide glue-- youcan force thin hide glue right trhough that joint, either with your thumb, or, better, with a small suction cup. moistne that whole area, a little bit, and I suspect the swelling wood will clamp it very effectively. I don't think you are in trouble at all...and I have had this happen, too... as well as several finished violins that came to me for repairs with a center seam popped. It happens.

Chet

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I have seen a violin with a narrow piece of a braided cloth material (?linen) stuck along the whole length of the back joint.

In that case, it was clear that the reinforcement was done post-varnishing.

You may wish to consider doing the same with a strong cotton or linen tape.

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Every (professional quality) violin I have owned has been a 1 piece back - not because it was a prerequisite, just because of coincidence. Now that I am venturing into violin making, I chose to use a 1 piece because it is familiar to me. I am now learning that I may be also avoiding a tricky procedure My violin maker teacher also uses 1 piece tops (though I understand that 2 piece center line is very handy with the rest of the process!)

It sounds like you still have a violin there - keep it going!

CB

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quote:


Originally posted by:
COB3

Of course it is fixable. Just not as fun as "everything went right on the first try."


Okay, I have calmed down, taken a deep breath, and had a good look at the situation. I've seen that if I press lightly with my fingers while holding the plate in front of the light, I can get the void to close (no light showing through), so that's encouraging. I think it is in fact a very small misfit, void, whatever, not pinholes (it's very hard to capture in a photo). So I think the first thing I will try is getting some hide glue into the crack, and moistening the area around it, in the hope that will provide enough clamping pressure to get it glued together. If that doesn't work, I'll move on to gluing a couple of pillars on either side of the crack and use a gentle clamp with hide glue. I'll judge the success of the repair by whether I can continue graduating without having it open up again. I'll also proceed carefully, and be attentive in case a similar situation should crop up in another part of the seam (god, I HOPE not!). I will not give in to panic.

Thanks for all the advice, and especially for putting up with a newbie without the experience to know just how much to worry about something. Obviously, the next time I see this happen, or something like it (and you know it will, don't you?), I'll be able to assess things more calmly, having seen it before. Maybe someday I'll be asked to repair a fiddle with a crack, and I'll be thankful I learned this stuff early. Dues must be paid, either in cash to a school, or some other way...

I'll post how things go. Won't have time to try anything till tomorrow night, tho...

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That's the attitude...

There isn't enough space in the world to contain the books which can list everything which can "go wrong" with violin-making.

St Murphy is the true patron saint of violin-making...

So, the attitude to take when something goes wrong (which it will) is that it is old news, albeit with a new text. Any violin-making manual is as true a compass to the "real world" as a James Bond novel is to life-on-the-street for the common man.

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To everyone: I have been working on several tops and backs, and every one has opened during hollowing. I am convinced that I have a bad bunch of hide glue, since every joint opened cleanly (i.e. no wood splinters etc.) and I do not think they all could have been poorly prepped and planed. The glue was from International Violin, although I do not mean to criticize them them in any way. They just re-package and sell what they get, and I have always been very pleased with their service and products. I just ordered a new batch of glue from Joel at Tools for Workiing Wood, and will report soon. Doug

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Doug, have you otherwise tested this glue?

If you glue together a couple scraps of maple and break them apart you'll get an instant read on whether there's a technique problem or a glue problem. If it's a glue problem IVC would I'm sure be grateful to know it before they sell even more of it.

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During making process, both of my top and back plates are subjected to thorough wetting several times and I have not experienced any center joint failure. First of all, I always test the glue whenever I get a new bag of it in. Put a drop of warm glue on your finger and press together. If you feel no tackyness, the glue is not processed correctly and should be thrown to the can. I remember I threw the whole bag of dry glue I got from International Violin 6 years ago. The high tackiness is an indication of the quality of the hide glue. I don't care about the commercial spaghetti strength they specify. I have done mechanical testing (tensile and shear) of hide glue on spruce and maple.

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Tim, I'm looking at your solution (I won't call it a repair because it is just part of the process of building anything). Glad you got it sorted out. Totally off topic and the reason for this post, I wanted to compliment you on how well you matched the two sides of maple. In some areas it looks like a 1 piece back.

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Thanks very much, Keld. I did spend some amount of time trying to figure out just how I wanted to match it up, and realized at one point that until it wasn't completely predictable, because the flames do wander a bit through the thickness. In the end, I chose one or two flames as my guide, and went with that. I noticed that some of the flames would line up so that it was "dark" on one side and "light" on the other, sort of like a negative mirror-image. I thought that looked neat. The overall effect is rather pleasing, I think...

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